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National Grid warns inflexible generators as summer demand forecast to hit more new lows

Transmission system demand is forecast to dip to new lows this summer, but National Grid has once again insisted it has the tools necessary to manage.

This morning saw the release of National Grid’s Summer Outlook, an annual document wherein it models likely supply and demand as well as any issues that may arise.

Today’s outlook revealed that the transmission system operator (TSO) has forecast both peak and minimum transmission system demand to be lower than last year, courtesy of increasing distributed generation such as wind and solar.

Daytime minimum demand could fall by a further 1.1GW to 20.1GW, while minimum summer demand is expected to be some 600MW lower than last year at 17GW. Peak system demand is expected to be 33.7GW.

Particular points of strain on National Grid’s need to balance the system are forecast to fall between the end of June and early July.

Supply and demand impacts

Such low demand on the transmission system – distributed power is connected to the country’s raft of distribution networks, so is merely seen on the transmission system as reduced demand – is likely to have wide ranging effects on the country’s diverse portfolio of electricity generation assets.

National Grid again expects that it will instruct some inflexible generators, typically nuclear, CHP and some wind and hydro facilities, to turn off this summer as production from the UK’s ~13GW of operational solar caters for an increasing percentage of demand.

Meanwhile, pumped storage facilities may be asked to move water back up their facilities to artificially increase power demand, and trading with neighbouring states via interconnectors will push power elsewhere.

National Grid also expects some coal plants to be temporarily mothballed this summer as low wholesale prices, pushed downwards by increased solar and wind generation on the system, renders them uneconomical. This will however contribute towards a reduced level of total available generation which the TSO expects to occur from June through August.

Another record-setting summer?

National Grid also nodded towards some of the records that were broken last summer, a spell which for many became emblematic of the wider transition of the power sector.

While a new peak solar generation record was set on Friday 26 May 2017, National Grid recorded daytime demand lower than that of the previous night for the first time on 25 March 2017. Graphs from the TSO included in today’s outlook illustrate solar and wind’s role in pushing demand so low, with National Grid adding that further incidents of this kind could occur again this summer.

But perhaps the overriding message in today’s report is that National Grid has assembled a suite of tools that, combined with accurate forecasting, has enabled the system operator to adequately balance the system as required.

Central to these tools are mechanisms like demand turn-up, while this summer will be the first that National Grid has 200MW of battery storage capacity procured via the Enhanced Frequency Response mechanism at its disposal.